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The use of baffles for directing the air around the cylinders with closely spaced fins proved very effective in increasing the over-all heat-transfer coefficient provided that the spacing was not appreciably less than that for maximum heat transfer.
This report is the summary of a literature survey and analytical study performed by the Armour Research Foundation for NEPA on the subject of the effect of turbulence promotion on forced convection heat transfer and fluid friction.
Results are presented on drag tests of six bodies of revolution with systematically varying shapes and with a fineness ratio of 5. The formes were derived from source-sink distributions, and formulas are presented for the calculation of the pressure distributions of the forms. The tests were made in the N.A.C.A. variable-density tunnel over a range of values of Reynolds number from about 1,500,000 to 25,000,000. The results show that the bodies with the sharper noses and tails have the lowest drag coefficients are based on the two-thirds power of the volume. The data show the most important single characteristic of the body form to be the tail angle, which must be fine to obtain low drag.
As part of the wing-fuselage interferences investigation in progress in the N.A.C.A. variable-density wind tunnel, a method of eliminating the interference burble associated with critical midwing combinations was investigated. The interference burble of the critical midewing combination was shown to respond to modifications at the nose of the juncture and to be entirely suppressed with little or no adverse effect on the high-speed drag by special leading-edge fillets.
First-order relations were obtained for attenuation of shock and flow deflection outward along the shock. These relations probably conform closely to physical fact, provided the entrance slope is small. These relations contain an error, but become exact as the radial coordinate approaches inifinity. The error is thus probably of the second order over the entire shock front.

Report

United States. National Advisory Committee for Aeronautics

Published: 1944

Total Pages: 32


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